In many applications, such as on board ships, there is a need for a light-weight, reliable portable engine-pump unit. For example, such units are used as portable fire fighting pumps or dewatering pumps. Present-day portable units of the indicated type generally use a two-stroke gasoline engine because of its light weight. However, the use of a fuel such as gasoline involves inherent dangers because of the inflamability of the gasoline.
A rotary piston engine (Wankel engine) is ideal for units of the indicated type because of its light weight, its compactness, and its high speed characteristics. Also, this engine would be safer because its combustion characteristics permit it to be run on diesel-type low volatility fuels easier than a two-stroke gasoline engine. However, their use has not become a reality because of the difficulty in starting an engine with a diesel-type fuel. In applications such as fire fighting it is extremely important that the unit be quickly available in case of an emergency and that the unit can be started with certainty.
It is the general object of the invention to provide a reliable starting means for a portable engine-pump unit. In accordance with the invention there is provided a portable engine pump unit in which a rechargeable electric storage battery may be used for the starting means and means are provided for maintaining this battery fully charged while it is being held in a stored condition.
Briefly stated, the portable engine-pump unit of the invention is provided with a portable frame means on which the pump, the engine and the starting means, including the battery, are mounted. There is provided a stationary holder for releasably receiving the frame means in a stored position, the frame means being movable into and out of the stored position as desired. There is also provided an electric circuit means for supplying a charging current to the battery and power supply means for supplying electrical power to the charging current circuit means. There are provided a pair of cooperable contact means on the power supply means and the charging circuit means adapted to be moved into electrical contact when the portable frame means is mounted in the stored position so as to supply the charging current. The contact means are constructed and arranged to be moved out of electrical contact when the portable frame means is removed from the stored position to disconnect the charging current from the battery.
In accordance with another aspect of the invention there is provided means for raising the temperature of the diesel-type fuel supplied to the engine so as to improve the combustion efficiency of the rotary piston engine. In a typical reciprocating piston diesel engine air is drawn into the cylinder and is compressed to a very high ratio of about 14:1 to 25:1. This high compression causes the air in the cylinder to be heated to a temperature of 700.degree.-900.degree. C. This high temperature causes spontaneous ignition of the diesel fuel that is injected into the cylinder. On the other hand, a rotary piston engine only has a combustion ratio of about 7:1 thereby providing a temperature rise in the combustion chamber of only about half that of the typical diesel engine. Accordingly, there are problems in both starting and running a rotary piston engine with a diesel-type fuel. In accordance with the invention there is provided various means for obviating this problem by raising the temperature of the diesel-type fuel so as to increase the combustibility thereof and thereby improve the running and starting performance of a rotary piston engine using diesel-type fuel.
One form of fuel heating means in accordance with the invention comprises an electric resistance heater for the fuel contained in the carburetor fuel bowl. This heater is energized from the engine starter battery and there is preferably provided a thermoswitch means to control the heating action so as to maintain a desired temperature of the fuel in the fuel bowl. Also, there is provided a switch means for energizing the fuel bowl heater only when the portable frame means is removed from the stored position and preventing any heating action while the portable frame means is maintained in the stored position.
In accordance with another feature of the invention there is provided an electric heater immersed in the engine fuel tank for heating the fuel therein and an electric heater located to supply heat to the expansion valve for a pressurized fuel supply of propane used for starting the rotary piston engine. There is provided circuit means for energizing those electric heaters from the starting battery.